Replacing the cylinder head gasket Cummins ISF2.8 GAZelle NEXT

Replacing the cylinder head gasket Cummins ISF2.8 (GAZelle NEXT)

We replace the gasket because of coolant or engine oil leaks at the joints between the cylinder head and the cylinder block.

To replace the cylinder head gasket, the engine must be removed, since the timing drive chain has to be dismantled. Access to the valve train on an engine installed in the vehicle is impossible.

Tools and materials required

To carry out the work you will need: 8, 10, 15 and 16 mm sockets, a torque wrench, an extension bar, a ratchet handle, a set of screwdrivers, a set of flat feeler gauges, a metal straight edge, and a locking tool to hold the pulley.

Materials and parts used:

New cylinder head gasket (MLS, multi-layer steel). It is recommended to use an original part or a quality equivalent (e.g. Victor Reinz, Goetze). The gasket with two notches (part no. 4943051) is approximately 1.15–1.20 mm thick and is intended for the standard piston protrusion.
New cylinder head bolts (recommended, as the bolts are usually stretch bolts).
Engine oil (for lubricating the bolt threads and seals).
Timing case cover gasket (replace if necessary).
Chain tensioner cover gasket (if necessary).
Coolant and engine oil (for topping up after assembly).
Rags, cleaner for removing remnants of the old gasket.

Important: when using a multi-layer steel (MLS) gasket, no sealant should be applied. The block and head surfaces must be perfectly clean and dry.

Preparation and removal

We prepare the vehicle for the work. We remove the engine.

EGR valve and cooler assembly on the engine — This assembly is removed first — the exhaust gas recirculation valve together with the cooler

We remove the exhaust gas recirculation valve together with the cooler. We remove the turbocharger. We remove the cylinder head cover (see the article Replacing the cylinder head cover gasket).

Upper part of the engine with the head cover removed — Once the cover is off, the rockers and cylinder head bolts are accessible

We set the No. 1 cylinder piston to TDC on the compression stroke (see the article Setting No. 1 cylinder to TDC).

We unscrew the five bolts securing the timing case cover.

Five bolts around the timing case cover — The timing case cover is secured by five bolts — these must be unscrewed

We remove the cover.

Exposed timing case cavity — The removed cover exposes the gasket and the internal drive components

We remove the gasket. A new gasket must be fitted on reassembly.

Timing case cover sealing gasket — This gasket is not reused — a new one is fitted during assembly

We unscrew the two bolts securing the chain tensioner cover.

Two bolts on the chain tensioner cover — The chain tensioner cover is held by two bolts

We remove the cover.

Chain tensioner cover removed — Beneath the cover is the chain tensioner plunger

We extract the tensioner plunger.

Tensioner plunger withdrawn from its bore — The plunger is withdrawn carefully so as not to damage its surface

We secure the chain by tying it with wire.

Timing chain tied with wire — The wire stops the chain slipping off the crankshaft sprocket

We slacken the bolt securing the trigger wheel and the camshaft sprocket while holding the shaft to prevent it turning.

Spanner on the camshaft sprocket bolt — The camshaft must be held stationary while the bolt is slackened

We fully unscrew the bolt securing the phase sensor trigger wheel and the camshaft sprocket.

Trigger wheel and sprocket bolt withdrawn — Once the bolt is out, neither the crankshaft nor the camshaft may be turned

Caution: after unscrewing the bolt securing the phase sensor trigger wheel and the camshaft sprocket, neither the crankshaft nor the camshaft may be turned, so as not to disturb the valve timing.

We remove the wheel.

Phase sensor trigger wheel removed from the shaft — The trigger wheel is removed together with the camshaft sprocket

We remove the sprocket together with the chain from the camshaft nose.

Camshaft sprocket with the chain fitted — The sprocket is removed together with the chain, without letting it slip off

We extract the spacer washer so as not to lose it.

Thin spacer washer on the shaft nose — It is best to put the washer aside straight away — it is easily lost

We secure the timing chain together with the sprocket on the engine.

Chain and sprocket secured on the engine — The secured chain will prevent the valve timing being disturbed when the head is removed

We remove the thermostat housing. We slacken the bolt securing the chain damper to the cylinder head.

Chain damper bolt on the cylinder head — This bolt secures the chain damper to the cylinder head

And unscrew the bolt.

Chain damper bolt unscrewed — Once the bolt is unscrewed, the damper can be moved aside

We unscrew the two bolts securing the timing case to the flywheel housing.

Two bolts in the lower part of the timing case — These two bolts join the timing case to the flywheel housing

Location of the timing case securing bolts.

Diagram with numbered timing case bolts — The diagram shows the location of all the timing case securing bolts

We unscrew the bolts securing all the rockers.

Bolts holding the rockers on their shafts — Each rocker is secured by its own bolt

We extract the bolts.

Rocker bolts withdrawn from the head — The removed bolts are kept separately so they are not mixed up on reassembly

We remove the rockers.

Rockers removed from their shafts — The removed rockers are inspected for wear before refitting

We extract the tappets.

Tappets withdrawn from their bores — The tappets are withdrawn carefully so they do not drop into the oil galleries

We withdraw the rocker shaft supports.

Rocker shaft supports removed from the head — The rocker shaft supports are removed after the tappets have been extracted

We unscrew the ten cylinder head securing bolts.

The location of the cylinder head securing bolts is shown in the figure below.

Diagram with numbered cylinder head bolts — Following this diagram, the bolts are unscrewed and then tightened in the reverse order

We untie the camshaft sprocket and chain from the cylinder head and remove the head together with the intake pipe, exhaust manifold and vacuum pump, keeping the timing chain taut.

Important: immediately after removing the cylinder head, secure the timing chain with wire in the taut position so that it does not slip off the crankshaft sprocket.

We remove the cylinder head gasket.

Old cylinder head gasket lying on the block — The old gasket is examined: the leak marks help to pinpoint the cause of the fault

Inspection and preparation of surfaces

We inspect the mating surfaces of the head and cylinder block. We clean the mating surfaces of remnants of the old gasket.

Cleaning the block face of gasket remnants — The block surface must be clean and dry before the new gasket is fitted

We check the cylinder head for distortion.

Straight edge and feeler gauge on the head face — The gap between the straight edge and the head face must not exceed 0.05 mm

We place the straight edge on its edge on the head surface, first along the middle, then diagonally, and in every position of the straight edge we measure the gap between the head surface and the straight edge with a feeler gauge. If the gap is greater than 0.05 mm, the head is replaced.

Fitting the new gasket and reassembly

We take the new gasket out of its packaging immediately before fitting. We fit the new gasket to the cylinder block with the sealing bead facing upwards.

We refit the cylinder head in the reverse order, observing the following:

Remove oil or coolant from the threaded holes for the cylinder head bolts that entered after the head was removed.
Lubricate the bolts with engine oil.
Screw in the cylinder head bolts and the two timing case bolts by hand, but do not tighten them.

Tightening the cylinder head bolts is carried out on a cold engine in the order shown in the figure below.

Diagram with the cylinder head bolt tightening sequence numbers — The bolts must be tightened strictly to this diagram, in three stages

Tightening consists of three stages:

First stage – tighten the bolts to 60 N·m;
Second stage – turn the bolts a further 90°;
Third stage – turn the bolts a further 90°.

We tighten the two timing case securing bolts to 4 N·m.

We refit all the parts in the reverse order. We adjust the valve clearances (see the article Adjusting the thermal valve clearances). We refit the engine to the vehicle.